上海交通大学张绍东研究团队报道了具有拓扑手性的交织三聚笼型链烷。相关研究成果发表在2024年10月22日出版的《美国化学会杂志》。

索烃因其拓扑手性等独特特征而受到越来越多的关注。迄今为止，大多数工作都集中在由单环组成的链状结构上。由于缺乏有效的合成策略，多环化单体的链状物仍然很少。

该文中，研究人员报告了通过在适当长度的二胺连接体和三醛板之间以化学计量比进行动态亚胺缩合，以高产率一锅法合成交织的三聚笼链状物。笼链状结构的形成是由板的有效6倍π-π堆叠驱动的。单体笼和三聚体笼链烷可与可逆亚胺化学相互转化，后者在热力学上更受青睐。

使用基于拓扑结构的统计模型，首先发现交织链状结构的形成概率比其链状异构体的形成概率高20%。当考虑到芳香族板的π-π堆叠提供的强模板效应来完善这个纯数学模型时，它表明交织结构是优势物种的，几乎排除了后者的形成。

尽管由非手性笼单体组成，但通过手性高效液相色谱（HPLC）和圆二色性（CD）光谱揭示了交织三聚体链烷的拓扑手性，交织笼链烷的单晶X射线衍射（XRD）分析也揭示了一对两种拓扑对映体。

概率分析辅助理论基础将为指导拓扑复杂结构的有效综合提供设计理论基础。

附：英文原文

Title: Interwoven Trimeric Cage-Catenanes with Topological Chirality

Author: Lihua Chen, Zhenghong Chen, Weihao Wang, Chenhao Chen, Yoshiaki Kuboi, Chi Zhang, Chenfei Li, Shaodong Zhang

Issue&Volume: October 22, 2024

Abstract: Catenanes have gained increasing attention for their unique features such as topological chirality. To date, the majority of works have focused on catenanes comprising monocyclic rings. Due to the lack of efficient synthetic strategy, catenanes of multiannulated monomers remain scarce. Here, we report the one-pot synthesis of an interwoven trimeric cage-catenane in high yield by dynamic imine condensation between diamine linkers of suitable length and trialdehyde panels in stoichiometry. The formation of cage-catenane is driven by the efficient 6-fold π–π stacking of panels. The monomeric cage and trimeric cage-catenane are interconvertible with reversible imine chemistry, with the latter thermodynamically being more favored. Using a topology-based statistical model, we first reveal that the formation probability of the interwoven catenane surpasses that of its chain-like isomer by 20%. When this pure mathematical model is refined by taking into account the strong template effect provided by the π–π stacking of aromatic panels, it shows that the interwoven structure emerges as the dominant species, almost ruling out the formation of the latter. Although composed of achiral cage monomers, the topological chirality of the interwoven trimeric catenane is unraveled by chiral-high-performance liquid chromatography (HPLC) and circular dichroism (CD) spectroscopy, and single-crystal X-ray diffraction (XRD) analysis of the interwoven cage-catenane also reveals a pair of two topological enantiomers. Our probability analysis-aided rationale would provide a design rationale for guiding the efficient synthesis of topologically sophisticated structures.

DOI: 10.1021/jacs.4c10104

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c10104